1. Field of the Invention
The present invention relates to 3D rotational angiography (3D RA), and more particularly relates to synchronized 3D rotational angiographic systems and processes for enhanced soft tissue imaging with optimized for X-ray dose reduction and improved patient throughput.
2. Description of the Related Art
Angiography refers generally to the capture and representation of blood vessels, in particular, the arteries and veins of the human body by means of X-ray imaging. 3D rotational angiography (3D RA) includes acquiring a series of 2D X-ray projection images (raw images) recorded at different projection angles, and using a sub-set of the series of raw images to generate a 3D RA image data record of the blood vessels to be examined. 3D RA may be implemented on an X-ray system including a rotational C-arm to acquire the series of projection images along a circular orbit while a continuous injection of contrast agent (contrast bolus) is administered into the vasculature of the patient under examination. The conventional C-arm X-ray system includes an X-ray source and X-ray sensor or detector (or image intensifier (XRII) camera) that is mounted on the C-arm in an opposing position with respect to the source, for acquiring the 2D projection images. A 3D reconstruction processor receives the series of 2D projection (raw) images and implements a process such as cone beam reconstruction to generate a 3D reconstruction of the vasculature under study.
Typically, the 3D reconstructed images or angiogram are studied by clinician(s) to support interventional procedures, e.g., an endovascular procedure such as percutaneous transluminal coronary angioplasty. During the endovascular procedure, 2D fluoroscopy is carried out with the same X-ray C-arm system used for the 3D angiographic procedure, preferably with the 3D reconstruction available for viewing on a split screen or a second monitor. The 2D fluoroscopy also includes “roadmapping,” which is 2D fluoroscopic imaging and supports navigation and maneuvering of the catheters through the patient's vasculature. In a roadmapping procedure, a contrast-enhanced fluoroscopic image is captured and stored, and that image is subtracted from subsequent images. The result is a static display of the vascular structures, typically displayed in white, while the catheter appears in black. The roadmapping, however, may display positional ambiguity. To remedy such positional ambiguity, the clinician must inject a contrast agent into the vasculature to opacify the vessels.
In cardiac angiography, where the heart and its coronary arteries are under study, it is problematic for recording purposes that the blood vessels are subject to constant movement as a result of the heartbeat rhythm. ECG gating is known for use in 3D RA imaging of the ventricles and coronary arteries, and arteries proximate the heart. For example, Onno Wink, et al., Coronary Intervention Planning Using Hybrid 3D Reconstruction, MICCAI 2002, LNCS 2488, pgs. 604-611 (Springer Verlag 2002) discloses a 3D RA process where 2D raw images are synchronized with the cardiac rhythm using an ECG signal such that only the 2D projection (raw) images recorded during a low-movement phase of the cardiac cycle are used to reconstruct the 3D image data. U.S. Pat. No. 6,404,850, to Heinz Horbaschek, discloses a cardioangiography apparatus that carries out 3D RA and provides compensation for cardiac motion with a cardiac motion compensation unit, narrowing the imaging to a small volume that includes a region of interest, e.g., a stenosis.
Such conventional systems and techniques, however, tend to realize only a small amount of useable images taken during the 2d projection or fluoroscopic imaging. The X-ray source or emitter, however, typically exposes the patient to x-rays, continuously, or at least for all useable and non-useable 2D projection or raw images that are acquired. More particularly, during conventional ECG gating-based fluoroscopy, only a few raw 2D projection images may be used from the generally several hundred raw images recorded during a full rotation of the X-ray emitter (source) and detector unit (X-ray sensor). Not only is the patient (and clinician) exposed for each unusable 2D projection image (regardless of whether operating in continuous or pulsed mode), but also the reduction in the number of useable images from a set or scene can result in significant deterioration of the quality of the reconstructed 3D image with respect to spatial and contrast resolution.
In order to overcome such shortcomings of the prior art, an inventive 3D C-arm X-ray system for 3D RA, and processes for using the system are disclosed and described herein to provide for optimal dose reduction, accurate 3D reconstruction of the heart's chambers and/or coronary vasculature and faster patient throughput when utilized with an ECG triggering and corresponding acquisition of 2D raw projection images of same.